the best thing to do is to ride them and pay attention to ride differences and geo. differences. Quite frankly, it's not really important how different the actual fibers are, but rather how they are woven. The way the fibers are woven gives the bikes different ride characteristics, so two bikes made of the same exact carbon may ride completely differently. If you want a huge bb shell (i am assuming for stiffness), and don't mind not riding full carbon (and have the $$$$$ to do so), check out the Pinarello Dogma FP. It has some rediculously large BB shell, byt that's over most mortals' budgets. there is also a new carbon Pinarello called the 4:13 that has lots of oversized tubes, but i can't tell if it has the same oversized BB and shell. Check 'em out at
www.competitivecyclist.com.